.text
.globl _start
_start:
    # set ebp for backtrace
    # movl $0x0, %ebp
	mov fp, #0

    # move down the esp register
    # since it may cause page fault in backtrace
    # subl $0x20, %esp
	sub sp, sp, #0x20

    # call user-program function
    bl umain
	
spin:
    b spin

